In general, an optical analysis device analyzing and measuring characteristics of light such as light intensity or phase reacted with an object to be measured, phase, etc. may determine a state of the object to be measured such as amount, type, etc. according to reaction light. As such an optical analysis device, an absorbance analysis device obtaining a result by quantifying an amount of light that is absorbed and partially passes according to an aspect of an object to be measured, a spectrum analysis device obtaining a result by using an amount of light that is passed or absorbed according to a wavelength range, a fluorescence analysis device using a phenomenon that is excited by ultraviolet wavelength and emits light, etc. are used.
As an example of the above optical analysis device, Korean Patent Application Publication No. 10-2014-0029410 discloses “Method and apparatus for the measurement of the mass fraction of water in oil-water mixtures”, Korean Patent No. 10-0789724 discloses “Method and apparatus for monitoring oil oxidation in real-time by measuring fluorescence”, and Korean Patent No. 10-1229372 discloses “System for detecting excluded oil and method thereof”.
As described above, in a conventional optical analysis device analyzing an amount (concentration) of an object to be measured, in order to optimize a result value according to a measurement result, that is, in order to maximally obtain a measurement result or to extend a measurement range where a small amount of a sample is measured, as a state of reaction light varies according to an amount size of an object to be measured, a method of adjusting a temporal and spatial range that reacts with light according to a characteristic (type, amount, etc.) of the object to be measured, a method of adjusting sensitivity of an optical sensor measuring reaction light, and a method of adjusting intensity of a light source are reflected in a measurement system.
Specifically, first, a method of adjusting a temporal and spatial range that reacts with light is a method that is mainly used when measuring a small amount of a sample, and uses a method of increasing an optical path length so as to increase a space and a time which pass or react with an object to be measured. When an optical path length is increased, a minimum measurement limit capable of measuring a small amount of a sample is increased, as well as, a measurement resolution is also increased in a state such where reaction light intensity varies according to a sample state or small change in amount thereof. However, when an amount of a measurement sample is increased, reaction light reaches a saturation state, and thus additional process of physically decreasing an optical path length is required for measuring a high concentration. Accordingly, a measurement range is limited (narrow) when using a measurement device using a single optical path length.
Second, a method of adjusting sensitivity of an optical sensor measuring reaction light is a method used when a result state of reaction light according to an amount of a sample or sample type is provided, and is a method of setting the sensitivity of the optical sensor to a range where reacted light is received, and measuring the same. The above method requires additional optical part or electric part so as to measure an object to be measured which exceeds measurement sensitivity of an optical sensor since a measurement range is determined according to the measurement sensitivity (adjustable sensitivity) of the optical sensor. For example, in order to measure light intensity lower than measurement sensitivity, a method of amplifying a measurement signal is used. However, in a general optical sensor, an additional circuit for amplifying a current or signal is required since a measurement result is converted to an electric signal (current or voltage). However, in a case of a minute current, a measurable limit value becomes small even though the signal is amplified since a signal-to-noise ratio of the measured signal is small.
Third, a method of adjusting intensity of a light source that induces an optical phenomenon of an object to be measured in an optical measurement device is a method of relatively increasing a size of an optical signal measured by irradiating a higher amount of light to obtain a high signal for a small amount of an object to be measured. The above method may adjust a measurement area (range) without requiring an additional optical part, an electric amplifier, a structure adjusting an optical path length. However, when using a single light source, a measurement range may be adjusted but adjusting an amount of light is limited. Accordingly, the range that is fundamentally measured is limited. In addition, an accurate measurement is available when an amount of light of the light source which is fundamentally emitted has to be fixed so as to obtain a quantitative result by dividing an optical signal varying according a measurement amount, and thus a reaction value (characteristics of fluorescent light) of an object to be measured which reacts according to an amount of adjusted light has to be provided in advance when the amount of light is adjusted for expanding a measurement range.